Hydrostatic pipe splicing method

ABSTRACT

A method and apparatus for containing an annular body of fluid about a sleeve spanning the abutting ends of pipe lengths, and firing a charge of propellant, such as fast burning smokeless powder, in the liquid so as to radially shrink the sleeve into sealing engagement with the pipe lengths. If desired, the pipe lengths can be internally supported to avoid the possibility of collapse. Hard annular elements may be interposed between the sleeve and the pipe length ends to produce better mechanical locking.

This is a continuation of application Ser. No. 024,761 filed Mar. 28,1979, now abandoned.

This invention relates generally to joining lengths of pipe and moreparticularly concerns a method and apparatus for hydrostatically forminga sleeve into a pipe splice.

A pipe line is conventionally formed by butt welding the ends ofsections of pipe. For example, a gas transmission pipe line may beformed of approximately 40 foot lengths of extruded aluminum pipe 4" indiameter and having 1/4" thick walls. Adjacent pipe lengths arecarefully welded to form gas tight joints. Such welds are difficult andexpensive to make at best, and inherently the welded areas becomesomewhat annealed, creating weak spots in the resulting pipe line.

There is a body of patent art suggesting the forming of pipe or tubeconnections by explosively driving a sleeve into intimate contact withadjacent ends of the lengths of the pipe or tube. U.S. Pat. No. Re.26,685--U.S. Pat. Nos.3,366,334--3,495,778--3,742,582--3,759,551--3,872,707 and 3,876,233represent aspects of this work. However, to applicant's knowledge, theseor similar techniques have not been used commercially for pipe splicing,probably because of a number of technical problems flowing from thegeneral approach of explosively driving a cold forming member to producethe desired connection.

Accordingly, it is the primary aim of this invention to eliminateexpensive, time-consuming welding for the making of gas tight pipesplices by providing a novel sleeve splice that avoids many of theproblems of the prior art.

It is an object of the invention to provide such a splice which allowsthe pipe to be spliced in end abutting contact, thus avoiding internalpipe discontinuities, and which requires no critical dimensioningpreparation of the splicing sleeve. A related object is to provide asplice as characterized above that does not depend on criticaltolerances between the pipe and the splicing apparatus since thesplicing force is exerted hydrostatically. It is another object toprovide such a splice in which the splicing force is created by firing acharge of powder, but which does not require critical placement of thecharge.

Another object is to provide a splice of the above type that resultsfrom a process that can be repeated if it is thought desirable. Afurther object is to provide a splicing process of the foregoingcharacter that can be performed under water on pipe that has been cutfor access or is otherwise already substantially in place.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in which:

FIG. 1 is a fragmentary perspective of a splice embodying the presentinvention;

FIG. 2 is an exploded perspective of the parts appearing in FIG. 1before the splice is made;

FIG. 3 is a longitudinal section of the apparatus used for making thesplice illustrated in FIG. 1; and

FIG. 4 is an end view of the structure appearing in FIG. 3.

While the invention will be described in connection with a preferredembodiment, it will be understood that I do not intend to limit theinvention to that embodiment. On the contrary, I intend to cover allalternatives, modifications and equivalents as may be included withinthe spirit and scope of the invention as defined by the appended claims.

Turning to the drawing, there is shown in FIG. 1 a splice 10 embodyingthe invention in which two pipe lengths 11 and 12 are brought into endabutting relationship and a sleeve 13, bridging the abutting ends of thepipe lengths 11, 12, is radially shrunk into sealing engagement with thepipe lengths. Preferably, substantially annular members such as ordinarypiano wire can be wrapped around the pipe length end as at 16, or fittedwithin the sleeve as at 17, before the ends of the pipe lengths 11, 12are slipped into the sleeve 13. Thus, when the sleeve 13 is radiallyshrunk into place, the annular members at 16, 17 are embedded in thematerials of the sleeve and pipe length ends to provide a mechanicallock against linear displacement.

In accordance with the invention, the splice 10 is made by slipping thesleeve 13 over the ends of adjacent pipe lengths, confining an annularbody of liquid, preferably water, about the sleeve 13, and firing acharge of propellant in the liquid so as to radially shrink the sleeve.In the illustrated embodiment, the annular body of water is confinedbetween a pair of end plates 21 and 22 that closely surround the pipelengths 11, 12 and abut the ends of the sleeve 13, and a cylindricalbody 23 sealed between the end plates 21, 22 so as to define a cavitybetween the end plates 21, 22, the sleeve 13 and the body 23. A tappedhole 24, which can be substantially water sealed by a screw 25, permitsthe cavity to be filled with water. Preferably, simple resilient liquidsealing members 26 are fitted between the end plates 21, 22 and thesleeve 13 and the body 23.

The end plates 21, 22 and cylindrical body 23 assembly is readilysecured together by a plurality of bolts 28 and nuts 29. A package ofpropellant 30 is inserted in the cavity before it is sealed and filledwith water, and electrical detonation leads 31 are run through a sealedhole in the body 23 to a battery 32 and a firing switch 33. The fluidmay be pressurized by other methods, i.e. a pump, the either internal orexternal to the cavity.

To give some idea of the scales involved, good experimental results havebeen obtained joining 4" diameter extruded aluminum pipe (T6 alloy 6061)that is nominally 1/4" thick. The sleeve, also aluminum, was fitted onthe pipe length ends with about 1/16" to 1/4" clearance. A propellantcharge of approximately 300 to 500 grains of Bullseye™ smokeless pistolpowder, packed in a waterproof bag, was utilized. Igniting the chargeresulted in shrinking the sleeve into gas tight sealing engagement withthe pipe length ends.

For guarding against internal collapse of the pipe lengths, a mandrel 35slightly longer than the sleeve 13 may be slid into the pipe lengths 11,12 for supporting the inside walls of the pipe lengths when thepropellant is discharged. A cable 36 fixed to one end of the mandrel 35permits the mandrel to be forcibly withdrawn after the splice is made.

The firing of the propellant 30 directly in the body of virtuallyincompressible liquid develops tremendous force on the sleeve 13 which,being the weakest element containing the liquid, deforms into thedesired configuration. This is plainly different from the use of anexplosive created gas pressure, acting through a liquid, for formingmetal as in U.S. Pat. No. 2,995,053.

It can now be seen that a splice 10 has been provided which allows thepipe to be spliced in end abutting contact, thus avoiding internal pipediscontinuities which can cause vortexes in the material beingtransmitted through the pipe or hang-up points for mechanical "pigs"used to clean or test the pipe. Since the splicing force is exertedhydrostatically, there are no critical mechanical tolerances to bemaintained. The placement of the charge 30 is also not critical sinceits actuation anywhere in the body of liquid produces an instantaneousand uniform shrinking force on the sleeve.

It will be appreciated that the splice 10 can be formed under water ifdesired on pipe already substantially in place. Furthermore, theoperation can be repeated at a given splice location since the parts arenot so distorted by a single splicing operation as to prevent arepetition of the process.

The structure illustrated and described above is intended to confirm andillustrate the principle involved. Commercial apparatus would desirablybe side-opening so as to fit over a continuous length of pipe at anyintermediate point.

I claim as my invention:
 1. A method of splicing pipe by sealing asleeve over the ends of adjacent pipe lengths comprising, incombination, the steps of slipping a closely fitted sleeve over the endsof adjacent pipe lengths, completely confining an annular body of liquidabout said sleeve with a rigid structure, and firing a charge ofpropellant in said body of liquid so as to radially shrink said sleeveinto sealing engagement with said pipe lengths.
 2. The combination ofclaim 1 including the step of interposing hard, substantially annularmembers between said sleeve and the ends of said pipe lengths beforefiring said charge so that said firing embeds said members in saidsleeve and said pipe lengths to provide mechanical locking therebetween.
 3. The combination of claim 1 in which pipe length ends areabutted, and including the step of supporting the inside walls of thepipe lengths against collapse during actuation.
 4. A method of splicingpipe by sealing a sleeve over the ends of adjacent pipe lengthscomprising, in combination, the steps of slipping a closely fittedsleeve over the ends of adjacent pipe lengths, completely confining anannular body of a substantially incompressible medium about said sleevewith a rigid structure, and firing a charge of propellant in said rigidstructure so as to radially shrink said sleeve into sealing engagementwith said pipe lengths.
 5. The combination of claim 4 including the stepof interposing hard members between said sleeve and the ends of saidpipe lengths before firing said charge so that said firing embeds saidmembers in said sleeve and said pipe lengths to provide mechanicallocking therebetween.
 6. The combination of claim 4 in which pipe lengthends are abutted, and including the step of supporting the inside wallsof the pipe lengths against collapse during actuation.